CN102172253B - A kind of method for preparing lactic acid bacteria direct-throwing type starter at normal temperature - Google Patents

Abstract

The invention provides a method for preparing a direct-vat-set(DVS) starter of lactic acid bacteria at normal temperature and aims to provide a method for preparing a DVS starter of lactic acid bacteria, which has the advantages of simple preparation process, low cost, high biomass and activity. The method comprises the following steps: applying lactose and glycerin on peeled and chopped steamed breads as a protectant, sterilizing, drying and using the peeled and chopped steamed breads as carriers; coating the bacterial suspension of lactic acid bacteria on the steamed bread carrier under a sterile condition to obtain the starter of lactic acid bacteria coated with the strain; and drying the starter of lactic acid bacteria coated with the strain by blowing at normal temperature and under the sterile condition to obtain the DVS starter of lactic acid bacteria. In the method, the lactose and the glycerin are applied on the steamed bread carriers as the protectant in the drying process of the steamed breads; simultaneously starch and proteins in the steamed breads can also well protect the lactic acid bacteria and the frozen damage is avoided; therefore, the starter is quite high in bacterial survival rate, activity and biomass. In addition, the method also has the advantages of simplicity, convenience for implementation and low cost.

Description

A kind of method for preparing lactic acid bacteria direct-throwing type starter at normal temperature

technical field

The invention relates to the field of microorganisms, and more specifically, relates to a method for preparing lactic acid bacteria direct-throwing starter at normal temperature.

Background technique

Due to the rich nutritional value and good health care function of fermented yogurt, as well as the improvement of the consumption level of our people and the popularity of health concepts, the production and sales of yogurt have shown a rapid growth trend in recent years, with an average annual growth rate of 25%. my country's largest fermented dairy product. In my country's fermented yogurt products, the starter used in more than 80% of the yogurt is a concentrated freeze-dried starter. Because the yogurt starter is mostly prepared by freeze-drying, the freeze-drying preparation starter process is relatively loaded down with trivial details, and the investment and operating costs of the equipment needed for freeze-drying are high, energy consumption is large, and the freeze-drying process time is long (typical freeze-drying The cycle needs at least more than 20h), so the product cost is very high, which is not conducive to industrialized production. Moreover, the freeze-drying method is likely to cause the loss of bacterial cells and affect the activity of the bacterial cells.

At the same time, although domestic research on freeze-dried yogurt starter has been developed for more than 30 years, and a large amount of manpower and material resources have been invested, no breakthrough has been made. Therefore, the vast majority of yogurt starters are purchased from well-known foreign starter companies, leading to the monopoly of the starter market by foreign companies, with an average price of up to 5 million yuan/ton, while the annual consumption of starter starters in my country is about 300 tons , The cost of introducing yogurt starter is as high as 1.5 billion yuan. Since my country's dairy processing enterprises all use imported direct-input yogurt starters, the production cost is relatively high (the cost of starters for fermented milk products per ton is more than 200 yuan), which limits the application of direct-injection yogurt starters in small and medium-sized dairy companies. use.

Therefore, finding a kind of process is simple, and cost is low, and the method that is suitable for the novel preparation lactic acid bacteria starter of my country's national conditions becomes the task of top priority.

Contents of the invention

The present invention aims to overcome the deficiencies in the prior art, and provides a method for preparing lactic acid bacteria direct-injection starter at normal temperature with simple preparation process, low cost, high biomass and activity, and industrialization.

The present invention realizes through following technical scheme:

A method for preparing lactic acid bacteria direct-throwing type starter at normal temperature, is characterized in that, comprises the steps:

(1) Preparation of lactic acid bacteria direct-injection starter carrier: Add lactose and glycerin as protective agents to peeled steamed buns, then sterilize with high-pressure steam at 121°C for 30 minutes, and then dry at 37°C as a carrier for later use;

(2) the lactic acid bacteria suspension is coated on the carrier obtained in step (1) under aseptic conditions, until the carrier is saturated, and the lactic acid bacteria starter coated with good strains is obtained;

(3) The prepared lactic acid bacteria starter coated with good strains in step (2) is aseptically air-dried at room temperature to obtain a lactic acid bacteria direct-throwing starter.

The mass addition of lactose is 1%-5% of the mass of steamed bread, and the volume addition of glycerin is 1%-5% of the mass of steamed bread.

The lactic acid bacteria in the step (2) are any one of Lactobacillus helveticus, Lactobacillus bulgaricus and Streptococcus thermophilus. All of the above strains can be obtained commercially or prepared by conventional methods. Among them, Lactobacillus helveticus can specifically use TS206 (Lactobacillus helveticus TS206, Lactobacillus helveticus 6024, etc.); Lactobacillus bulgaricus can use Lactobacillus bulgaricus 1.1480, Lactobacillus bulgaricus NCFB2772, etc.; Streptococcus thermophilus can use Streptococcus thermophilus 6038, Streptococcus 6217 et al.

When Lactobacillus helveticus is used, the method for preparing the suspension of Lactobacillus helveticus is: inoculate the Lactobacillus helveticus strain in the whey-modified medium composed of whey powder, glucose, yeast powder and water, and place it at 37°C Cultivate in an incubator for 24 hours; then centrifuge the fermentation broth at 1500rpm×20min at room temperature, discard the supernatant, obtain the precipitate, and obtain the Lactobacillus helveticus cell; finally dilute the Lactobacillus helveticus cell with sterile normal saline to obtain Lactobacillus helveticus suspension with cell concentration ≥ ^{10 9} cfu/ml; Among them, in the whey-improved medium, by mass percentage: whey powder is 10%, glucose is 0.5%, yeast powder is 0.5%, and the rest water.

The lactic acid bacteria direct-injection starter obtained in step (3) is rolled and pulverized, and then the pulverized lactic acid bacteria starter is passed through a 20-40 mesh sieve to obtain a lactic acid bacteria direct-injection starter with uniform particle size.

The present invention has following technical effect:

1. In the method of the present invention, protective agents such as lactose and glycerin are added to the steamed bread carrier, and at the same time, the steamed bread itself is rich in starch and protein, which has a good protective effect on lactic acid bacteria. In addition, in the process of preparing the direct-throwing starter, the bacteria are not freeze-dried but naturally dried, which avoids freezing damage. Therefore, the obtained starter has a high bacterial survival rate, activity and biomass. capable of industrialization. In the present invention, the initial concentration of lactic acid bacteria is more than or equal to ^{10 9} cfu/ml, and the bacteria content in the starter prepared by using steamed bread as a carrier can reach more than 10 ⁸ cfu/g, the survival rate of the starter bacteria can reach more than 60%, and the activity is very high , there was almost no loss in curdling time after a month of storage at room temperature.

2. The steamed bread carrier used in the present invention has a honeycomb structure, which is easy to absorb and coat bacteria on the one hand, and is also easy to dry on the other hand. The whole drying process can be completed within 12 hours, and the preparation method is fast, simple and easy.

3. In the method of the present invention, Chinese traditional food steamed buns are used as the carrier of lactic acid bacteria, that is, the suspension of lactic acid bacteria is adsorbed onto the sterilized steamed bun carrier, and then the steamed buns containing lactic acid bacteria are aseptically dried at room temperature, and finally pulverized to make powder without Expensive equipment, small investment, low energy consumption, greatly reducing production costs.

4. Yeast powder and glucose are added to the whey medium for cultivating Lactobacillus helveticus used in the method of the present invention, which provides necessary growth factors and carbon sources for the growth of Lactobacillus helveticus. The cell concentration of Lactobacillus helveticus cultivated by the medium can reach 10 ⁹ cfu/ml.

Detailed ways

The present invention will be described in detail below in conjunction with specific embodiments.

Example 1

(1) Prepare Lactobacillus helveticus cells with whey medium:

10% whey powder, 0.5% glucose, 0.5% yeast powder and the rest of water are mixed according to the mass percentage to prepare the whey-improved medium.

Lactobacillus helveticus TS206 (Lactobacillus helveticus TS206) strains were inoculated in the above-mentioned whey-modified medium, and cultured in a 37°C incubator for 24 hours. Then centrifuge the fermentation broth at 1500rpm×20min at room temperature, discard the supernatant, obtain the precipitate, and obtain the Lactobacillus helveticus cells, dilute the Lactobacillus helveticus cells with normal saline, and prepare the cell concentration of 10 ⁹ cfu/ml The bacterial suspension was stored in a 4°C refrigerator for later use.

(2) Preparation of steamed bread carrier: Peel the steamed bread and cut it into 2 × 2 × ^2cm blocks, then add lactose and glycerin to the peeled steamed bread block by dropping, steamed bread: mass percentage concentration is The 50% lactose solution: glycerol is 100g: 4ml: 3.5ml, sterilized by high pressure steam at 121°C for 30 minutes, and placed in an oven at 37°C after sterilization as a carrier for later use.

(3) The standby Lactobacillus helveticus bacteria suspension obtained in step (1) is directly coated on the steamed bread carrier obtained in step (2), until the steamed bread carrier is saturated, and the starter coated Lactobacillus helveticus is obtained .

(4) Drying the starter coated with Lactobacillus helveticus prepared in step (3) aseptically blown at room temperature for 12 hours, and drying completely to obtain the Lactobacillus helveticus direct-throwing starter.

(5) crushing the dried Lactobacillus helveticus direct-injection starter prepared in step (4), and passing through a 20-40 mesh screen to obtain a finished product of Lactobacillus helvetica direct-injection starter powder with uniform particle size.

(6) Determination of bacterial content in Lactobacillus helveticus direct-introduction type starter: first take by weighing 1g of Lactobacillus helvetica direct-injection type starter bacterium powder that step (5) makes and put into 10ml 10% aseptic whey culture medium In the process, rehydrate at 20°C for 30 minutes, dilute with normal saline, ^and then use MRS solid medium double-layer plates to count the bacteria. More than 60%, the activity is very high, and there is almost no loss of curdling time after storage at room temperature for one month.

(7) Prepare yogurt with the prepared Lactobacillus helveticus starter: take 100ml of fresh milk, add 4g of sucrose, sterilize at 100°C for 15 minutes, take 2g of the Lactobacillus helveticus direct-injection starter powder prepared in step (5) and add it to the milk Mix well, shake well, ferment at 37°C for 8 hours, after the fermented milk curds, put it in a refrigerator at 4°C and cook for 12 hours to make yogurt. The yogurt curd prepared by using the prepared Lactobacillus helveticus starter has good curds, moderate acidity, thick texture and fine taste.

Example 2

(1) Prepare Lactobacillus bulgaricus thalline with MRS medium:

Inoculate Lactobacillus bulgaricus 1.1480 strain in MRS medium and culture at 37°C for 24 hours, then centrifuge the fermentation broth at room temperature at 3000rpm×30min, discard the supernatant and take the precipitate to obtain Lactobacillus bulgaricus cells, dilute Bulgaricus bulgaricus with normal saline Lactobacillus cells were made into a bacterial suspension with a cell concentration of 10 ¹⁰ cfu/ml, and stored in a 4°C refrigerator for later use.

(2) Preparation of steamed bread carrier: Peel the steamed bread and cut it into 2 × 2 × ^2cm blocks, then add lactose and glycerin to the peeled steamed bread block by dropping, steamed bread: mass percentage concentration is The 50% lactose solution: glycerin ratio is 100g: 6ml: 1.5ml, sterilized by high pressure steam at 121°C for 30min, and placed in an oven at 37°C after sterilization as a carrier for later use.

(3) The standby Lactobacillus bulgaricus suspension obtained in step (1) is directly coated onto the steamed bread carrier obtained in step (2) by dropping until the steamed bread carrier is saturated, and the coated Bulgaricus Lactobacillus starter.

(4) The starter coated Lactobacillus bulgaricus prepared in step (3) was aseptically air-dried at room temperature for 12 hours, and completely dried to obtain the Lactobacillus bulgaricus direct-throwing starter.

(5) crushing the dry Lactobacillus bulgaricus direct-injection starter prepared in step (4), and passing through a 20-40 mesh sieve to obtain a finished product of Lactobacillus bulgaricus direct-injection starter powder with uniform particle size.

(6) Determination of bacterial content in Lactobacillus bulgaricus direct-injection starter: first weigh 1 g of Lactobacillus bulgaricus direct-injection starter bacterial powder prepared in step (5) and put it into 10 ml sterile MRS medium, and set it at 20° C. Rehydrated for 30 minutes, diluted with normal saline, and counted the mixed bacteria on the MRS solid medium plate. Finally, the concentration of Lactobacillus bulgaricus was measured to be about 10 ⁹ cfu/g, and the survival rate of the starter bacteria could reach more than 65%, with a high activity High, with little loss in curdling time after a month of storage at room temperature.

(7) Prepare yogurt with the prepared Lactobacillus bulgaricus starter: take 100ml of fresh milk, add 4g of sucrose, sterilize at 100°C for 15min, take 2g of Lactobacillus bulgaricus direct-injection starter powder prepared in step (5) and add it to the milk Mix well, shake well, ferment at 37°C for 8 hours, after the fermented milk curds, put it in a refrigerator at 4°C and cook for 12 hours to make yogurt. The yogurt curd produced by using the prepared Lactobacillus bulgaricus starter has good effect and strong milky fragrance.

Example 3

(1) Prepare Streptococcus thermophilus thalline with MRS medium:

Inoculate Streptococcus thermophilus 6038 strains in MRS medium, culture at 37°C for 24 hours, then centrifuge the fermentation broth at room temperature at 3000rpm×30min, discard the supernatant and take the precipitate to obtain Streptococcus thermophilus cells. Streptococcus thermophilus cells were diluted with saline to prepare a bacterial suspension with a cell concentration of 10 ¹⁰ cfu/ml, and stored in a 4°C refrigerator for later use.

(2) Preparation of steamed bread carrier: Peel the steamed bread and cut it into blocks of 2×2×2cm ³ , then add lactose and glycerin to the steamed bread block by dropping, steamed bread: 50% by mass concentration Lactose solution: glycerol is 100g: 5ml: 3ml, sterilized by high-pressure steam at 121°C for 30 minutes, and placed in an oven at 37°C after sterilization as a carrier for later use.

(3) The standby Streptococcus thermophilus suspension obtained in step (1) is directly coated onto the steamed bread carrier obtained in step (2) by dropping until the steamed bread carrier is saturated, and the coated Fermentation agent for Streptococcus thermophilus.

(4) Aseptically air-dry the starter coated Streptococcus thermophilus prepared in the step (3) at room temperature for 12 hours, and completely dry to obtain the Streptococcus thermophilus direct-throwing starter.

(5) crushing the dried Streptococcus thermophilus direct-injection starter prepared in step (4), and passing through a 20-40 mesh sieve to obtain a finished Streptococcus thermophilus direct-injection starter powder with uniform particle size.

(6) Determination of bacterial content in Streptococcus thermophilus direct-throwing type starter: first take by weighing the Streptococcus thermophilus direct-throwing type starter bacteria powder 1g that step (5) makes is put into 10ml aseptic MRS medium, Rehydrate at 20°C for 30 minutes, dilute with normal saline and then use MRS solid medium plate to count mixed bacteria. Finally, the concentration of Streptococcus thermophilus is about 10 ⁹ cfu/g, and the survival rate of the starter bacteria can reach more than 65%. , high activity, almost no loss of curdling time after storage at room temperature for one month.

(7) Prepare yogurt with the prepared Streptococcus thermophilus starter: take 100ml of fresh milk, add 4g of sucrose, sterilize at 100°C for 15 minutes, take 2g of the Streptococcus thermophilus direct-injection starter powder prepared in step (5) and add Put it into the milk, shake it well, and ferment it at 37°C for 8 hours. After the fermented milk curds, put it in a refrigerator at 4°C and cook it for 12 hours to make yoghurt. The yogurt curd produced by using the prepared Streptococcus thermophilus starter has good effect and strong milky aroma.

The method for preparing lactic acid bacteria direct-injection starters at normal temperature adopted in the present invention can be applied to the production of various lactic acid bacteria direct-injection starters, and has strong popularization value.

Claims (4)

1. prepare the method for lactic acid bacteria throw type leaven under the normal temperature, it is characterized in that, comprise the steps:

(1) preparation of the directly putting type fermented agent carrier of lactic acid bacteria: will add lactose and glycerine on the steamed bun piece of peeling as protective agent, then 121 ℃ of high pressure steam sterilization 30min are afterwards, for subsequent use as carrier in 37 ℃ of oven dry; Wherein, the quality addition of lactose is the 1%-5% of quality of steamed bread, and the volume addition of glycerine is the 1%-5% of quality of steamed bread; Lactose is to add take the form of the lactose solution of mass percent concentration as 50%;

(2) with the lactic acid bacteria bacteria suspension on the coated carrier that obtains to step (1) under the aseptic condition, until carrier is saturated, make the lactic acid bacteria fermenting agent that is coated with good bacterial classification;

(3) with the aseptic forced air drying of lactic acid bacteria fermenting agent room temperature of the coated good bacterial classification that makes in the step (2), obtain the lactic acid bacteria throw type leaven.

2. prepare the method for lactic acid bacteria throw type leaven under the normal temperature according to claim 1, it is characterized in that, the lactic acid bacteria in the step (2) is any in Lactobacillus helveticus, lactobacillus bulgaricus, the streptococcus thermophilus.

3. the method for preparing the lactic acid bacteria throw type leaven under the normal temperature according to claim 2, it is characterized in that, when using Lactobacillus helveticus, the method for preparing the Lactobacillus helveticus bacteria suspension is: in the whey improved culture medium that is comprised of whey powder, glucose, dusty yeast and water, place 37 ℃ of incubators to cultivate 24 hours the Lactobacillus helveticus bacterial classification inoculation; Afterwards that zymotic fluid 1500rpm * 20min under normal temperature is centrifugal, abandoning supernatant is obtained precipitation, namely obtains the Lactobacillus helveticus thalline; With SPSS dilution Lactobacillus helveticus thalline, obtain cell concentration 〉=10 at last ⁹The Lactobacillus helveticus bacteria suspension of cfu/ml; Wherein, in the whey improved culture medium by mass percentage: whey powder is 10%, and glucose is 0.5%, and dusty yeast is 0.5%, the water of surplus.

4. the method for preparing the lactic acid bacteria throw type leaven under the normal temperature according to claim 1, it is characterized in that, step (3) is obtained the lactic acid bacteria throw type leaven roll pulverizing, then the lactic acid bacteria fermenting agent after will pulverizing is crossed 20-40 purpose screen cloth, obtains even-grained lactic acid bacteria throw type leaven.